Growth and characterization of ZnTe single crystal via a novel Te flux vertical Bridgman method
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Growth and characterization of ZnTe single crystal via a novel Te flux vertical Bridgman method Min Jin*
, Wen-Hui Yang, Xiang-Hu Wang, Rong-Bin Li, Ya-Dong Xu, Jia-Yue Xu*
Received: 10 July 2020 / Revised: 13 August 2020 / Accepted: 16 August 2020 Ó GRINM Bohan (Beijing) Publishing Co., Ltd 2020
Abstract In this work, an II–VI group semiconductor zinc telluride (ZnTe) single crystal is prepared by a novel vertical Bridgman method using Te as flux. The initial mole ratio of Zn/Te = 3:7 is designed for raw material synthesis. ZnTe polycrystalline combined with rich Te is effectively fabricated through rocking technique at 1100 °C. A U 25 mm 9 65 mm ZnTe boule is successfully grown under a * 40 °Ccm-1 temperature gradient with a growth speed of 5 mmday-1. The as-grown ZnTe crystal has a standard 1:1 stoichiometric ratio and pure F43m phase structure. The maximum transmittance perpendicular to (110) plane is about 64%, and the band gap (Eg) is tested to be 2.225 eV. Terahertz (THz) examination results demonstrate that the time of the highest THz signal is around 17 ps and the frequency of the highest THz transmission is about 0.78 THz, implying that the ZnTe crystal grown by the present Te flux vertical Bridgman method has a good feasibility for THz application. Keywords ZnTe crystal; Te flux; Vertical Bridgman method; Terahertz property
Min Jin and Wen-Hui Yang contributed equally to this work. M. Jin*, X.-H. Wang, R.-B. Li College of Materials, Shanghai Dianji University, Shanghai 201306, China e-mail: [email protected] W.-H. Yang, Y.-D. Xu State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China J.-Y. Xu* School of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai 201418, China e-mail: [email protected]
1 Introduction Among II–VI group semiconductors, zinc telluride (ZnTe) has become more attractive in recent years. Beneficial from its wide band gap, ZnTe crystal might be suitable for various optoelectronic device applications, such as solar cells, light-emitting diodes (LED), laser diodes (LD), THz emitters, detector devices [1–9]. However, the growth of large-size and high-quality ZnTe crystal is always a problem to this day, which restricts its further development remarkably. Frankly speaking, the relatively high melting point of ZnTe (* 1295 °C) and serious Zn volatilization are regarded as main problems in producing ZnTe crystals [10, 11]. In order to obtain ZnTe crystals, many kinds of techniques have been explored in the past, including liquidencapsulated kyropoulos (LEK) method, vertical gradient freezing (VGF) method, liquid-encapsulated vertical gradient freezing (LE-VGF) method, traveling solvent melting zone (TSMZ) method, physical vapor transport (PVT) technique, seeded vapor-phase free growth (SVPFG) method, etc. [12–20]. Among these approaches, the vapor process is considered not proper for large ZnTe crystal fabrication. Besides, ZnTe crystal grown from stoichiometric melt in enclose
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